What I believe is, when the souls aren't properly evolved, they might just pass by their twin souls without even a second glance... It takes a long time, many cycles of life and death, to master the lessons meant for every soul and find 'the one'.. When twin souls finally unite, they are liberated from this cycle.

I'd like to correct myself regarding something... 'Time is an illusion'... Awareness can dawn upon at any moment.. So it'might' take a long time or no time at all. Now, I am happy with what I've written. :)